KR20070081725A - Plasma display apparatus and image processing method there of - Google Patents

Abstract

A plasma display apparatus and an image processing method thereof are provided to enhance gradation representation performance by preventing a dual error diffusion pattern noise due to a conventional multi-channel mode. A plasma display apparatus includes an image signal receiver(410) and a half-tone unit(430). The image signal receiver divides plural pixels into at least two pixel regions, divides external image signal data into plural channels according to the pixel regions, synchronizes the divided channels with a clock signal, and outputs the synchronized channels. The half-tone unit performs an error diffusion process on data of an image signal which is transmitted from the image signal receiver, for each channel. The half-tone unit adjusts the error diffusion direction in the pixel regions along lines.

Description

Plasma Display Apparatus and Image Processing Method Thereof

1 is a view showing a method for implementing an image of a conventional plasma display device.

2A is a graph comparing luminance characteristics of a plasma display device and a cathode ray tube.

2B is a graph showing inverse gamma correction in a conventional plasma display device.

3A and 3B illustrate an error diffusion method of a conventional plasma display panel.

4 schematically illustrates a plasma display device according to the present invention;

5 is a block diagram showing an example of a halftone part according to the present invention;

6 shows an example of a block diagram for performing error diffusion in accordance with the present invention.

7 is a view for explaining a pixel area and an error diffusion method according to an embodiment of the present invention.

8 is a view for explaining an error diffusion method according to another embodiment of the present invention.

9A and 9B are views illustrating comparison of screens of error diffusion patterns of the plasma display device according to the present invention.

***** Explanation of symbols for main parts of drawing *****

410: image signal receiving unit 420: inverse gamma correction unit

430: halftone unit 440: subfield mapping unit

450: plasma display panel module

The present invention relates to image processing of a display device, and more particularly, to a plasma display device and an image processing method thereof for improving the speed and quality of the image processing.

In general, a plasma display panel is a partition wall formed between a front panel and a rear panel to form a unit discharge cell, and each cell includes neon (Ne), helium (He), or a mixture of neon and helium (Ne + He). An inert gas containing a main discharge gas such as and a small amount of xenon is filled. A plurality of unit discharge cells described above are gathered to form one pixel. For example, a red (R) cell, a green (G) cell, and a blue (B) cell may form one pixel. When a high frequency voltage is applied to such a unit discharge cell to discharge, an inert gas generates vacuum ultra violet rays and emits phosphors formed between the partition walls to realize an image. Such a plasma display panel has a spotlight as a next generation display device because of its thin and light configuration.

1 is a view showing a method for implementing an image of a conventional plasma display device.

As shown in FIG. 1, the plasma display apparatus divides one frame period into a plurality of subfields having different discharge times, and emits a plasma display panel in a subfield period corresponding to a gray value of an input image signal. An image is implemented.

Each subfield is divided into a reset period for uniformly generating a discharge, an address period for selecting a discharge cell, and a sustain period for implementing gray scale according to the number of discharges. For example, when the image is to be displayed with 256 gray levels, the frame period (16.67 ms) corresponding to 1/60 second is divided into eight subfields.

In addition, each of the eight subfields is divided into a reset period, an address period, and a sustain period. Here, the sustain period is increased at a rate of 2n (n = 0, 1, 2, 3, 4, 5, 6, 7) in each subfield. As described above, since the sustain period is changed in each subfield, gray levels of an image can be realized.

The brightness characteristics of the plasma display according to this are as shown in FIG. 2A.

2A is a graph comparing luminance characteristics of a plasma display device and a cathode ray tube.

As shown in FIG. 2A, a cathode-ray tube (CRT) and a liquid crystal display (LCD) express a desired gray level by controlling the displayed light in an analog manner with respect to an input video signal. , Typically has nonlinear luminance characteristics. In contrast, since the plasma display device expresses gray scales by modulating the number of light pulses using a matrix array of discharge cells that can be turned on / off, the plasma display apparatus has a linear luminance characteristic. The gray scale expression method of the plasma display device is called a PWM (Pulse Width Modulation) method.

In this case, the display device, such as a cathode ray tube (CRT), because the brightness characteristics compared to the display current is proportional to 2.2 multipliers, the input external video signal such as a broadcast signal transmits a signal corresponding to the inverse of the 2.2 multiplier. Therefore, the plasma display apparatus having the linear brightness characteristic needs to perform inverse gamma correction on an image signal input from the outside. This inverse gamma correction will be described with reference to FIG. 2B.

2B is a graph illustrating inverse gamma correction in a conventional plasma display apparatus.

In FIG. 2B, the target luminance represents an ideal inverse gamma result to be corrected, the actual luminance is a measured luminance value as a result after the inverse gamma correction, and the PDP luminance is less than or equal to the measured luminance value 3 in the absence of inverse gamma correction. It is shown.

As shown in FIG. 2B, the target luminance is expressed as luminance values having different levels of 61 gray levels from '0' to '60'. In contrast, the actual luminance is expressed by only eight luminance values of 61 gray levels from '0' to '60'. Therefore, when the inverse gamma correction is performed in the plasma display device, there is a problem in that it is impossible to express enough gray scales in a dark area, thereby generating a contour noise in which images are aggregated.

In order to express the insufficient gray level of the PDP, a half tone method such as a dithering method or an error diffusion method is used. Among these, an error diffusion method is as follows.

3A and 3B illustrate an error diffusion method of a conventional plasma display panel.

3A is a diagram for spatially explaining a conventional method of error diffusion in one channel mode, and FIG. 3B is a diagram for spatially explaining an error diffusion method in two channel mode, which is an example of multiple channels.

As shown in FIGS. 3A and 3B, the error diffusion method is a method for spatially correcting an error that is discarded by causing an error generated when a corresponding pixel is quantized to affect neighboring pixels. .

Referring to FIG. 3A, the error diffusion method in one channel multiplies neighboring pixels, i.e., each error value generated in three pixels (a, b, c) of the previous line and the adjacent pixel (d) by a specific coefficient. Subsequently, error values obtained by multiplying the coefficients are added to the center cell (i) and then quantized. Thereafter, the error value generated by the quantization is stored in the line memory again and repeated for every pixel.

This error diffusion method enables particularly good representation in moving images and does not generate constant pattern noise generated by using dithering methods.

However, in the case of displaying the still image in the error diffusion method, there is a problem in that the stationary pattern is displayed similarly to the dithering method. This stopped pattern appears as an error diffusion pattern accumulated at a specific gradation because the error diffusion coefficient that is multiplied by the decimal value is set constant. In addition, when the luminance difference of the real gray scales is large, the error diffusion pattern may be quite strong, resulting in pattern noise. This is especially true in dark screens with many low gradations.

In addition, such noise is further exacerbated in the multi-channel mode for realizing the high speed driving required as the display device becomes larger.

That is, in such a multi-channel mode, the video signal is divided into CH1 and CH2 in a two channel mode as shown in FIG.

More specifically, the first channel CH1 multiplies each error value generated in neighboring pixels, that is, three pixels (a, b, c) of the same channel of the previous line by the pixel (d) next to the specific channel, by a specific coefficient. The error is spread to the center cell (i). The second channel CH2 is likewise specific to each error value occurring in neighboring pixels, i.e., three pixels (a ', b', c ') of the same channel of the previous line, each of the error values occurring at the next pixel (d') of the channel. By multiplying the coefficients, the error is spread to the center cell (i ').

In such a multi-channel mode, the error is further deepened by error diffusion in the same pattern for each channel. Moreover, when the noise is intensified, a problem arises that the quality of image quality is further degraded as it is easily recognized by the human eye.

SUMMARY OF THE INVENTION In order to solve such a problem, an object of the present invention is to provide a plasma display device and an image processing method thereof capable of improving the speed of image processing.

Another object of the present invention is to provide a plasma display device and an image processing method thereof capable of improving the quality of image quality.

The technical problem of the present invention is not limited to the above-mentioned thing, and another technical problem to be achieved by the present invention will be clearly understood by those skilled in the art by the effect of the configuration of the present invention.

In accordance with another aspect of the present invention, a plasma display device divides a plurality of pixels corresponding to a screen into at least two pixel areas, and divides external image signal data into a plurality of channels according to the pixel areas. A video signal receiver for synchronizing and outputting a channel of one to a clock signal and a halftone unit for error diffusion of data of the video signal transmitted from the video signal receiver for each channel.

The image signal receiving unit may divide a plurality of pixels corresponding to the screen into two pixel areas, divide the image signal data into two channels according to the pixel area, and synchronize the image signal data to one clock signal for output. .

In addition, the halftone unit is characterized in that for adjusting the error diffusion direction in the pixel area according to the line.

In addition, the halftone unit is characterized in that the boundary portion where the two or more pixel areas neighbor each other overlap and error diffusion.

In addition, the boundary portion is characterized in that more than 8 pixels.

In addition, the boundary portion is characterized in that more than 16 pixels.

The image processing method of the plasma display apparatus according to the present invention for achieving the above object is divided into a plurality of pixels corresponding to the screen into at least two pixel areas, and the external image signal data into a plurality of channels according to the pixel area A video signal receiving step of dividing and synchronizing the plurality of channels to a single clock signal and outputting the same, and a halftone step of error diffusion of data of the video signal transmitted in the video signal receiving step for each channel.

In the receiving of the video signal, the plurality of pixels corresponding to the screen may be divided into two pixel areas, and the video signal data may be divided into two channels according to the pixel area to be synchronized with one clock signal and output. do.

In addition, the halftone step is characterized in that for adjusting the error diffusion direction in the pixel area according to the line.

In the halftone step, error diffusion is performed by overlapping boundary portions of the two or more pixel areas neighboring each other.

In addition, the boundary portion is characterized in that more than 8 pixels.

In addition, the boundary portion is characterized in that more than 16 pixels.

Hereinafter, with reference to the accompanying drawings will be described in more detail the configuration of the plasma display panel according to the present invention.

4 is a schematic view showing a plasma display device according to the present invention.

As shown in FIG. 4, the plasma display device according to an embodiment of the present invention includes an image signal receiver 410, an inverse gamma correction unit 420, a halftone unit 430, a subfield mapping unit 440, and a plasma. And a display module 450.

The image signal receiver 410 divides a plurality of pixels corresponding to the screen into at least two pixel areas, divides external image signal data into a plurality of channels according to the pixel area, and synchronizes the plurality of channels to one clock signal. The inverse gamma correction unit 420 outputs the result. Here, the video signal receiver 410 of the present invention distinguishes channels according to screen regions differently from the prior art, which will be described in detail later with reference to FIG. 5.

The inverse gamma correction unit 420 inversely gamma corrects the image signal data transmitted from the image signal receiver 410 and linearly converts the luminance value displayed in the gray value of the input image signal. Here, the inverse gamma correction unit 420 of FIG. 4 includes an inverse gamma correction unit for each channel, but is not limited thereto. Inverse gamma correction may be performed through one inverse gamma correction unit.

The halftone unit 430 diffuses the image signal data transmitted from the inverse gamma correction unit 420 into neighboring pixels by spreading an error component corresponding to an error diffusion coefficient for each channel, thereby finely adjusting the luminance value displayed according to the grayscale value. Adjust to improve the gradation expression.

The subfield mapping unit 460 maps an image signal input from the halftone unit 430 to a preset subfield mapping table.

The data signal processed as described above is transmitted to the plasma display panel module 450 through a data driver (not shown) to implement an image of the plasma display panel.

Here, the halftone part and the error diffusion method of the present invention for dividing the image signal data according to the divided screen region into multiple channels as described above will be described in detail with reference to FIGS. 5 and 6.

5 is a block diagram showing an example of a halftone unit according to the present invention.

As shown in FIG. 5, the halftone unit according to the present invention includes, for example, an error diffusion coefficient lookup table storage unit 431, a line storage unit 432, an image signal delay unit 433, and an error diffusion execution unit 434. It can be seen that it is made to include.

The error spreading unit 434 of the halftone unit 430 according to an embodiment of the present invention is assigned to the fractional value of the grayscale value of the inverse gamma corrected data for each channel according to the grayscale value of the image signal data for each channel. An error component multiplied by each error diffusion coefficient is spread to neighboring cells.

In this case, as shown in FIG. 5, an error diffusion coefficient lookup table storage unit 431 is provided to store information of each error diffusion coefficient allocated according to each grayscale value in advance.

Here, the error diffusion coefficient lookup table storage unit 431 may be provided inside or outside the halftone unit 430.

Thereafter, the error diffusion execution unit 434 receives error diffusion coefficient information from the error diffusion coefficient lookup table storage unit 431 and performs error diffusion for each channel. The method of performing such error diffusion is described in detail with reference to FIG. 6. .

6 is a diagram showing an example of a block diagram for performing error diffusion of the present invention.

As shown in FIG. 6, the error diffusion method is a method for spatially correcting an error that is discarded by causing an error generated when the corresponding pixel is quantized to affect neighboring pixels.

Here, the error diffusion method multiplies each error value generated in neighboring pixels by a specific coefficient, adds the error values obtained by multiplying the coefficients to the center cell value, and then performs quantization. Thereafter, the error value generated by the quantization is stored in the line memory and repeated for every pixel.

That is, as shown in FIG. 6, the error diffusion block repeatedly outputs a luminance value closest to the target luminance by repeatedly performing a spatial feedback routine. In more detail, in FIG. 6, the operation may be represented by Equations 1 and 2 below.

Here, the parameters of Equations 1, 2 and 6 are defined as follows.

n represents the current frame.

F (i, j) is a gray level value input after the inverse gamma correction.

Q block is a quantization block.

B (i, j) is the quantized grayscale value.

E (i, j) is the error that occurs in quantization.

f (i, j) is a value obtained by adding a quantization error value to an input grayscale value after inverse gamma correction.

That is, f (i, j) is a value obtained by multiplying the error value of the pixel neighboring F (i, j) in the current frame by the error diffusion coefficient h (i, j) in the H block.

Subsequently, the line storage unit 432 of FIG. 5 stores the inverse gamma corrected image signal in units of lines. In addition, the line storage unit 432 stores the gray scale value of the image signal in which the error diffusion is performed, and repeats it every pixel.

The image signal delay unit 433 delays the image signal in order to reflect the new gray scale value that is error-diffused to the neighboring cell using the error diffusion lookup table 431.

Here, the error diffusion execution unit 434 according to the present invention differentiates image signal data according to two or more pixel areas corresponding to the effective screen area for each channel and performs error diffusion to reduce pattern noise and provide high-speed driving. This can be enabled, which will be described with reference to FIG. 7.

7 is a diagram for describing a pixel area and an error diffusion method according to an exemplary embodiment of the present invention.

As illustrated in FIG. 7, a plurality of pixels corresponding to a screen area where an image is implemented may be divided into at least two pixel areas.

That is, for example, a 1920 * 1080 Full HD screen is divided into a left area (ED.1) and a right area (ED.2), and image signal data and a right area (ED.2) corresponding to the left area (ED.1). The video signal data corresponding to each channel may be divided into channels to transmit a signal in a multi-channel mode.

In this case, the multi-channel mode is a technique of dividing the video signal data into a plurality of channels and synchronizing the channel with one clock signal to output the video signal data transmission speed.

This multi-channel mode not only can easily realize high resolution but also solve the problem of clock margin. In addition, as it becomes possible to drive at high speed, it is possible to drive by lowering the frequency, thereby reducing the burden on high frequency processing.

Here, the present invention distinguishes the channel according to the screen area in the multi-channel mode differently from the prior art, thereby greatly reducing the noise appearing in the existing multi-channel mode.

More specifically, as shown in FIG. 7, the first channel includes image signal data corresponding to pixels in the left area ED.1 of the screen, and the second channel includes image signal data corresponding to pixels in the right area ED.2 of the screen. By dividing into, each channel is synchronized with one clock signal and outputted, thereby enabling high-speed driving.

In addition, by dividing the image signal data corresponding to each divided pixel region into channels and error diffusion for each channel, it is possible to prevent the aggregation of noise appearing in the same pattern for each channel in the existing multi-channel mode. Accordingly, there is an effect that can improve the quality of the image implemented by the display device.

Further, in an embodiment of the present invention, more preferably, a boundary portion where two or more pixel areas neighbor each other may overlap and error spread. That is, as shown in FIG. 7, the predetermined pixel area OL of the boundary between the left pixel area ED.1 of the screen and the right pixel area ED.2 of the screen may overlap and diffuse in error.

By overlapping a part of the divided screen pixel area, the error diffusion can remove not only noise that may occur at the boundary portion but also smoothly implement the screen.

In addition, the error diffusion by overlapping the pixel regions may prevent noise appearing due to unstable error diffusion at the initial error diffusion.

That is, in performing the error diffusion method, error values of pixels gradually accumulate to reflect more stable error values, thereby increasing reliability of error diffusion. However, when the first error diffusion is started, the error is diffused only by the error values of the initial pixels, so that a stable pattern does not appear and noise appears. This can be prevented by overlapping the error.

In this case, the predetermined pixel area of the boundary portion is 8 pixels or more, thereby minimizing pattern noise. More preferably, the image quality may be improved by optimizing the pattern noise to 16 pixels or more in a predetermined pixel area of the boundary portion.

In addition, by controlling the direction of error diffusion for each line during error diffusion, it is possible to reduce the pattern noise of error diffusion, as shown in FIG.

8 is a view for explaining an error diffusion method according to another embodiment of the present invention.

As illustrated in FIG. 8, for example, a plurality of pixels corresponding to a screen area where an image is implemented may be divided into at least two pixel areas, and image signal data corresponding to the area may be divided into a plurality of channels.

That is, for example, the screen area of 1920 * 1080 Full HD is divided into the left area (ED.1) and the right area (ED.2), and the image signal data and the right area (ED.2) corresponding to the left area (ED.1). ) Can be transmitted in a multi-channel mode by dividing image signal data corresponding to channels into channels.

More specifically, as shown in FIG. 8, the video signal data corresponding to the pixel of the left area ED.1 of the screen is the first channel, and the video signal data corresponding to the pixel of the right area ED.2 of the screen is the second channel. By dividing into, each channel is synchronized with one clock signal and outputted, thereby enabling high-speed driving.

In addition, by dividing the image signal data corresponding to each divided pixel region into channels and error diffusion for each channel, it is possible to prevent the aggregation of noise appearing in the same pattern for each channel in the existing multi-channel mode.

Here, in another embodiment of the present invention, the error diffusion direction may be adjusted for each pixel line when the error diffusion is performed for each pixel region, that is, for each channel. That is, for example, error diffusion may be performed in a zigzag manner by changing the error diffusion direction for each pixel line.

As such, by adjusting the direction of error diffusion, pattern noise appearing when error diffusion is performed in the same direction can be achieved to realize a higher quality image.

The effect of reducing the pattern noise appearing on the screen according to the present invention described above is as shown in FIG.

9A and 9B are diagrams illustrating screens of error diffusion patterns of the plasma display apparatus according to the present invention.

9A is a screen illustrating an error diffusion pattern appearing in a two-channel mode which is an example of a multichannel mode in a conventional plasma display apparatus, and FIG. 9B is an error that appears in a two-channel mode that is an example of a multichannel mode in a plasma display apparatus of the present invention. This screen shows a diffusion pattern.

9A and 9B, the error diffusion pattern in the conventional multichannel mode illustrated in FIG. 9A performs error diffusion by dividing adjacent pixels into different channels. In this case, due to the same error diffusion pattern for each channel, the channel 1 and the channel 2 are displayed in a group of two pixels, and the double error diffusion pattern noise appears.

On the other hand, as shown in FIG. 9B, when the image signal data according to the divided pixel region is divided into channels and the error diffusion is performed for each channel, the error diffusion pattern is uniformly displayed in detail.

As such, the use of the error diffusion method according to the present invention can improve the gray scale expression power by removing the double error diffusion pattern noise according to the conventional multichannel mode.

Accordingly, the present invention has the effect of improving the quality of the image implemented by the display device by realizing high-speed driving of the display device to enable high resolution, as well as improving the image quality caused by the display device.

Such a configuration of the present invention is not limited to the above embodiment. That is, the number of divisions can be increased as the resolution increases, for example, not only dividing the pixel region into two regions, the right region and the left region.

In addition, the present invention can be used in the image signal processing of all display devices, such as LCD, DMD, Projector, FED, SED, as well as the plasma display device of the above embodiment can improve the reliability of the image processing.

As such, it will be understood by those skilled in the art that the above-described technical configuration may be implemented in other specific forms without changing the technical spirit or essential features of the present invention.

Therefore, the exemplary embodiments described above are to be understood as illustrative and not restrictive in all aspects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

As described above, the plasma display device and the image processing method thereof of the present invention have the effect of improving the speed of image processing.

In addition, the plasma display device and the image processing method thereof of the present invention have an effect of reducing noise appearing on the screen.

In addition, the plasma display device and the image processing method thereof of the present invention have an effect of improving the quality of the image quality.

In addition, the plasma display device and the image processing method thereof of the present invention have the effect of enabling high-speed driving to reduce the burden caused by the processing of high frequency.

Claims (12)

An image signal receiver for dividing a plurality of pixels corresponding to a screen into at least two pixel areas, dividing the external image signal data into a plurality of channels according to the pixel area, and synchronizing the plurality of channels to a single clock signal and outputting the same. ; And Halftone unit for error diffusion of the data of the video signal transmitted from the video signal receiver for each channel Plasma display device comprising a. The method of claim 1, The video signal receiver And dividing a plurality of pixels corresponding to the screen into two pixel areas, dividing the image signal data into two channels according to the pixel area, and synchronizing and outputting the same to one clock signal. The method of claim 1, The halftone portion And adjusting the error diffusion direction in the pixel area according to a line. The method of claim 1, The halftone portion And a boundary portion in which the two or more pixel areas neighbor each other overlap and error spread. The method of claim 4, wherein And the boundary portion is at least 8 pixels. The method of claim 5, And the boundary portion is 16 pixels or more. In the image processing method of the plasma display device, Receives a video signal that divides a plurality of pixels corresponding to a screen into at least two pixel areas, divides external image signal data into a plurality of channels according to the pixel area, and synchronizes the plurality of channels to a single clock signal for output. step; And Halftone step of error diffusion of the data of the video signal transmitted in the video signal receiving step for each channel Image processing method of the plasma display device comprising a. The method of claim 7, wherein The video signal receiving step Dividing a plurality of pixels corresponding to the screen into two pixel regions, and dividing the image signal data into two channels according to the pixel region and synchronizing and outputting the same to one clock signal. . The method of claim 7, wherein The halftone step is And the direction of error diffusion in the pixel area according to a line. The method of claim 7, wherein The halftone step is And the boundary portion where the two or more pixel areas neighbor each other overlaps and diffuses errors. The method of claim 10, And the boundary portion is 8 pixels or more. The method of claim 11, And the boundary portion is 16 pixels or more.

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